Light Problem

[BLUE49]

After wiring my '49 3100 I was driving it at nite and had the headlites on. After about 10 minutes I heard a click and headlites went out. After about a minute, a click, and lites are back on. Thought it was a loose wire and checked all headlite wiring. It continues to happen on a regular basis. Is it possible theres a resettable breaker in the switch? I am in the process of rewiring the headlites, using a relay to take the load off the switch. Any Ideas out there?

[Wrenchbender Ret]

Yes. There is a breaker built in the switch. It may be defective or if you have Haligen bulbs it is overloaded. Its a good idea to put relays on the headlight system. It takes the load off the switch & reduces voltage drop for brighter lights.

[_Ogre]

yes, there is a bi-metal breaker on most headlight switches and that is probably your problem
i googled 49 headlight switch and came up with this, not sure if it's a car or truck
but you can see the metal strip running thru the center; that is the bi-metal breaker

assuming you do not have an overload situation, you can bend the bi-metal strip a bit so that it doesn't kick out at light loads
if you have a new wire harness with a real breaker for the headlights you can bend it a lot so it never kicks out
you should only have your headlights on this breaker
i too believe in using relays but only on the high beam side of your headlights



this is a pic of the 55-59 headlight switch, it has 2 bi-metal switches for head and brake lights

[OrrieG]

I never knew that was an overload device. But I have never had one overload. This time around I used a lot of relays on stuff to reduce the loads on switches.

[BLUE49]

I'm replacing the switch and adding a relay, which is what I should have done to begin with. As usual you guys are great. Its always good to have my suspicions confirmed.

[mr48chev]

They nailed it. Adding the relays to the headlight circuit is the best move any of us can make when we convert to 12 V and then use headlights that draw quite a bit more amps. It helps save the whole headlight circuit from overload and especially the dimmer switch.

[Russell Ashley]

If you encounter this problem of your lights going off, a temporary fix that will get you home is to unplug one of your headlights. A single headlight won't draw enough current to trip the bi-metal strip.

[_Ogre]

Originally Posted by OrrieG

I never knew that was an overload device.

similar to a bi-metal strip in your house thermostat
power going thru the strip heats up the strip
too much power causes more heat and then the contact breaks
cooling down causes the contact to close

they do fatigue over time, thus i recommended bending it
if you have a new wiring harness; painless, ezwire, etc.. it will have a auto reset breaker in the panel
then you can bend the bi-metal strip on the switch to never open.
stock wiring has no protection for the headlight circuit other than the bi-metal strip on the switch

you don't want a fuse in the headlight circuit as it will blow and never reset
at midnight, in a narrow canyon, while running 55 mph, into a curve, oofda

[mr48chev]

Those strips are still there to protect the switch and circumnavigating the strip could quite possibly cause the switch to overheat and fail with the higher amp flow through the switch. The higher amp rated breaker in the fuse block most likely will be rated much higher than the switch it's self can handle for any length of time.

On my 71 GMC I was burning out dimmer switches about every four or five months after I switched to H-4 Halogen lights. After the headlight switch failed too I installed relays in the headlight circuits and had no more issues with either switch. Relays are very inexpensive and real easy to install so that should not be an issue.